Support rel material:binding syntax(define only)

src/prim-reconstruct.cc

@@ -1297,7 +1297,7 @@ static ParseResult ParseShaderInputConnectionProperty(std::set<std::string> &tab
   return ret;
 }
 
-// Rel with single targetPath
+// Rel with single targetPath(or empty)
 #define PARSE_SINGLE_TARGET_PATH_RELATION(__table, __prop, __propname, __target) \
   if (prop.first == __propname) { \
     if (__table.count(__propname)) { \
@@ -1320,6 +1320,11 @@ static ParseResult ParseShaderInputConnectionProperty(std::set<std::string> &tab
         continue; \
       } \
       PUSH_ERROR_AND_RETURN(fmt::format("`{}` target is empty or has mutiple Paths. Must be single Path.", __propname)); \
+    } else if (!rel.has_value()) { \
+      /* define-only. accept  */ \
+      __target = rel; \
+      table.insert(prop.first); \
+      DCOUT("Added rel " << __propname); \
     } else { \
       PUSH_ERROR_AND_RETURN(fmt::format("`{}` target must be Path.", __propname)); \
     } \

src/prim-types.hh

@@ -892,7 +892,8 @@ struct PrimMetas {
 // For backward compatibility
 using PrimMeta = PrimMetas;
 
-// Metadata for Attribute
+// Metadata for Property(Relationship and Attribute)
+// TODO: Rename to PropMetas
 struct AttrMetas {
   // frequently used items
   // nullopt = not specified in USD data
@@ -935,6 +936,8 @@ struct AttrMetas {
 // For backward compatibility
 using AttrMeta = AttrMetas;
 
+using PropMetas = AttrMetas;
+
 // Typed TimeSamples value
 //
 // double radius.timeSamples = { 0: 1.0, 1: None, 2: 3.0 }

tests/usda/material-binding-003.usda

@@ -0,0 +1,7 @@
+#usda 1.0
+
+def Xform "geom"
+{
+  rel material:binding
+
+}